#include<iostream>
using namespace std;
class product
{
	private:
		int num,quantity;
		double price;
	public:
		product(int,int,double);
		static int book_total_quantity;
		static double total_sale;
};
int product::book_total_quantity=0;
double product::total_sale=0;
product::product(int num,int quantity,double price)
{
	this->num=num;
	this->quantity=quantity;
	this->price=price;
	book_total_quantity+=quantity;
	if(num>20)
	{
		total_sale+=price*(double)quantity*0.75;
	}
	else
	{
		total_sale+=price*(double)quantity;
	}
}
